GFCI 2-wire Experiment

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kwired said:
What EGC? From the beginning of this in the other thread, we were presuming no grounded surfaces present in an electrically isolated tub. Throwing in a grounded object for the potential victim to contact or for current to pass to via the water changes all the parameters of the experiment, and if you do have such current flowing outside the GFCI protected conductors that is more then the trip threshold - you will trip the GFCI whether there is a EGC present or not at the GFCI location. Unless you have water with no impurities chances are with a 120 volt source the water is conductive enough to carry the necessary 4-6 mA necessary to trip the GFCI.
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I believe that FZ is separately asserting that if a working EGC is connected to the appliance in question and that EGC is connected to metal, even if only a terminal on the end of the cord, anywhere in the appliance where water can get at it, then current will flow to the EGC and the GFCI will trip.
Whereas if there is no EGC present (as simulated by his two wire experiment) there cannot be any current imbalance and so the GFCI will not trip.

The question of how much current will actually flow on a path through the water outside the appliance body, this will depend strongly on the geometry and the stated experiment will test only one set of conditions. Note that in the experimental setup one of the meter electrodes was closer to one of the conductor wires than the other wire was. This is definitely a worst case compared to a user at some distance from the appliance.

The way the meter was used, it gives us a very rough approximation of how much current would flow (compared to the total current) if a zero resistance person were bridging between the same two points in the water. Putting a foil on the end of each electrode and putting a 3K resistor in series with one meter lead would give a much better approximation.
 
GoldDigger said:
I believe that FZ is separately asserting that if a working EGC is connected to the appliance in question and that EGC is connected to metal, even if only a terminal on the end of the cord, anywhere in the appliance where water can get at it, then current will flow to the EGC and the GFCI will trip.
Whereas if there is no EGC present (as simulated by his two wire experiment) there cannot be any current imbalance and so the GFCI will not trip.
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That is my take on it.

He was struggling to prove what we already knew.
 
iwire said:
And Joe T was posting a video of himself dropping a hair dryer in a sink without tripping the GFCI. Really basic electrical knowledge.
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Yeah, but I'm so glad that Fiona is here to set us dummies straight. After all:


FionaZuppa said:
i dont say this too often, its just one of those things i keep to myself, very obvious that many on this forum, including some mods, dont really understand electricity all that well.
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GoldDigger said:
Note that in the experimental setup one of the meter electrodes was closer to one of the conductor wires than the other wire was. This is definitely a worst case compared to a user at some distance from the appliance.
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the experiment didnt have my Fluke probes in the water for amps test, i used another set of alligator clips, i then simply moved those around in the water to find some amps. the distance of those clips from the wire ends was more than the Fluke probe pic i posted.
 
FionaZuppa said:
actually, no i did not. if i were to measure amps of water one end of the wire would be directly connected to one amp probe.
the amp probes (less whatever body ohms you may hypothesize would be inline with probe) is the body in the experiment.
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FionaZuppa said:
the experiment didnt have my Fluke probes in the water for amps test, i used another set of alligator clips, i then simply moved those around in the water to find some amps. the distance of those clips from the wire ends was more than the Fluke probe pic i posted.
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Your meter probes were taking the place of the shock victim. I bet your meter has much lower resistance then a person would have, skewing the results compared to finding a way to measure the current flowing in the ham I suggested using as a simulated vicitm. You can't just put a resistor in line with a probe or the power source to simulate the vicitm, in a real situation the voltage applied to the victim will vary depending on their relationship to the input voltage probes in the water, which will also effect not only the amount of current through the victim but where in their body it flows.
 
FionaZuppa said:
you say "most L-N faults will trip OCPD", well, i guess my crude experiment doesnt fall into your "most" category. in my experiment it doesnt (even if you take out that 18k inline), OCPD is perfectly happy supplying amps to a faulty ckt. what type of fault is it when you have current flowing via non-intended path(s), or potentially a hazard path? why does everyone think a current fault has to be back to EGC? the experiment i have shown is parallel to L-N path in the water, not in series with L or N, etc. from the dryer perspective, the switch is in off position yet there is amps on the wire, is this not a fault of some type?

the fridge frame is something different, its not a liquid conductor commonly found in all resi bathrooms :thumbsup:
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I think you fail to understand that a GFCI has nothing to do with immersion of an appliance, or at least that is not the intent. Where immersion is a concern we have this:


http://www.ecmag.com/section/codes-standards/differences-between-gfci-idci-and-gfpe
 
GoldDigger said:
I believe that FZ is separately asserting that if a working EGC is connected to the appliance in question and that EGC is connected to metal, even if only a terminal on the end of the cord, anywhere in the appliance where water can get at it, then current will flow to the EGC and the GFCI will trip.
Whereas if there is no EGC present (as simulated by his two wire experiment) there cannot be any current imbalance and so the GFCI will not trip.

The question of how much current will actually flow on a path through the water outside the appliance body, this will depend strongly on the geometry and the stated experiment will test only one set of conditions. Note that in the experimental setup one of the meter electrodes was closer to one of the conductor wires than the other wire was. This is definitely a worst case compared to a user at some distance from the appliance.

The way the meter was used, it gives us a very rough approximation of how much current would flow (compared to the total current) if a zero resistance person were bridging between the same two points in the water. Putting a foil on the end of each electrode and putting a 3K resistor in series with one meter lead would give a much better approximation.
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I suggested in another thread that he do some experimenting like he has tried, and he did do it, but he did not accurately simulate the conditions we were discussing with what he set up. I don't remember exactly what was said but we were disagreeing on current flow through a person sitting in a electrically isolated tub of water and if an energized appliance were dropped into the tub. I suggested that person was definitely in a hazardous situation, but at same time they are not necessarily going to be electrocuted and that their body resistance plus distance of water between their body and the submersed voltage source would be high enough they are not going to have significant enough current flow through their body to be harmful. The experiment was not supposed to be about whether or not a GFCI would trip but simply how much current might the potential shock victim be subject to. I don't feel the tests he has done so far give us a realistic picture of what that may be because he does not have a very accurate victim body being measured. A victim body is not a fixed resistor, it has variable resistance over varying surfaces and distances, you likely get more current in one portion of said body then you get in other parts of same body. That said it is nearly impossible to determine whether a victim lives or dies in the incident, you can only say a certain amount of current at a particular voltage made it through various points. But I still believe he will get different test results trying to measure voltages and currents through various points in a ham then just through meter probes suspended at various points in the water.
 
FionaZuppa said:
an old house that has old occupants, for last 52yrs in the home they never had any 5-R's (EVER), its all 2-wire crud. ok, so we can only imagine that for many many years they have used cheaters and broken EGC pins off, yes? ok, well, now you come along and swap out a 1-R with a non-EGC'd 5-R GFCI and place a sticker on it that says "no EGC". great, "20 more then" <-- sarcasm btw. the folks are blind as a bat but notice now there's this 3rd hole in the receptacle, they really have no idea what that is, but what they might know is, must be safer to just stop breaking off the EGC pin of items they buy, because you told them the GFCI is safer. well, they are indeed safer, but not because of the missing EGC, yet for some reason they believe that extra pin makes them safer, but in the realm of reality the 5- GFCI (now a logical 1-) does not provide all of the hazard coverage a EGC'd 5- GFCI does. given the context as to why anyone is swapping out a 1-R with a 5-R GFCI, why provide the EGC pin? imho, block it out, or, provide EGC. for those who thought the amps would only flow between the two terminals of the appliance when it hots the water, thats a big WRONG as many of us know it, but some insisted no amps would flow across the unattached amp probes, and what did we find, amps in fact do flow, and in some scenarios the amps through unattached probes can be greater that the trip specs of GFCI class-A !
yes, its from the other thread that went south, so i provided some real experimental data.
you may have missed my reply in this thread about your comment in red. if the EGC is too far away (could be 4ft in a tub), the ohms across 4ft of bath water may be less than GFCI trip amps, so for those who agreed in other post, perhaps they were missing some data?
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You would be correct if simultaneous immersion of both body parts and appliances occurred far more than a hot energizing the case with no EGC. In that case yes I might agree with you. However, come reality, standing ground faults are far, far more common.

I have investigated over 45 accidental electrocutions, of which over a dozen were caused by 120 volts, A.C. In every case, the third wire ground was either non-existent or it had been interrupted at some point. Third wire grounds work! We have never observed an electrocution involving a double insulated tool or when a ground fault circuit interrupter (GFCI) was in place.
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http://paceforensic.com/pdfs/newsletter/KeepingPace-8.pdf



 
So I have a sink full of water with no metallic equipment attached, ie plastic water lines, drains and non metallic sink. The outlet is 2 wire but has a gfci receptacle and an appliance plug in. My stupid self has my hand in the water and I knock the appliance into the water.

I agree in this case the gfci will not trip however nor will I get a shock. If I were grounded then of course some of the current will go thru me and then trip the gfci.

Is this what is being argued? If so, I have actually done this. I dropped a lighted wp flood bulb and exposed socket into a plastic pail and put my hand in it. No shock with a 2 wire cord connected to a gfci. I then took a ground wire and stuck it in the water and the gfci tripped....

What are we saying here
 
FionaZuppa said:
you have to look at it the other way. stop being an electrician for just a minute.

if someone has 5-P and cant plug that in, they go "hmmm, wtf, why is that, my plug has this 3rd pin on it, what do i do (run to HD and ask nim-wad who advises to not break pin off but gives a cheater)". <-- ok, that was some asserted effort there, but it got the person thinking about why there is a diff, the plug just didnt fit the 1-R.

ok, option two, 5-R GFCI w/o EGC "hmm, plug right in, i am all good". <-- nope, not all good, w/o the EGC there that GFCI does not cover all the hazards that a 5-R GFCI should be covering, yet the user didnt for 1sec question plugging in the 5-P cap cord, and has no clue what the sticker means (if a sticker is even there any longer).

and in a 2-wire house where you do a swap out of 1-R to a 5-R GFCI w/o EGC, what does it matter if they use cheater or break EGC pins off, there is no EGC, right? breaking pin off at that point does not create more hazard, right? (well, breaking pin off may be bad if the two blades are not polarized, so a cheater is really best option, HD guy did good).
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I do agree, lets all stop being electricians and engineers for a moment and think like a novice:


What average person would think it a good idea to swim or bath with a plugged in appliance? What person will think, 'Well, I know I have a full functioning EGC so I will be ok doing that'
 
Dennis Alwon said:
So I have a sink full of water with no metallic equipment attached, ie plastic water lines, drains and non metallic sink. The outlet is 2 wire but has a gfci receptacle and an appliance plug in. My stupid self has my hand in the water and I knock the appliance into the water.

I agree in this case the gfci will not trip however nor will I get a shock. If I were grounded then of course some of the current will go thru me and then trip the gfci.

Is this what is being argued? If so, I have actually done this. I dropped a lighted wp flood bulb and exposed socket into a plastic pail and put my hand in it. No shock with a 2 wire cord connected to a gfci. I then took a ground wire and stuck it in the water and the gfci tripped....

What are we saying here
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That is what we were debating in another thread when I asked him to do some experimenting in an electrically isolated tub, I don't even remember what that thread topic actually was but his topic at that point was revolving around the need for GFCI's to need an EGC to work. I was trying to point out a person must have a voltage across them to have a current flow through them, resistance of the paths in question make all the difference in the world to the end results
 
mbrooke said:
I do agree, lets all stop being electricians and engineers for a moment and think like a novice:
What average person would think it a good idea to swim or bath with a plugged in appliance? What person will think, 'Well, I know I have a full functioning EGC so I will be ok doing that'
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no, lets think like "NEC", we dont know exactly what end users do, this NEC code attempts to cover the hazards the best it can.

Dennis Alwon said:
So I have a sink full of water with no metallic equipment attached, ie plastic water lines, drains and non metallic sink. The outlet is 2 wire but has a gfci receptacle and an appliance plug in. My stupid self has my hand in the water and I knock the appliance into the water.

I agree in this case the gfci will not trip however nor will I get a shock. If I were grounded then of course some of the current will go thru me and then trip the gfci.

Is this what is being argued? If so, I have actually done this. I dropped a lighted wp flood bulb and exposed socket into a plastic pail and put my hand in it. No shock with a 2 wire cord connected to a gfci. I then took a ground wire and stuck it in the water and the gfci tripped....

What are we saying here
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try again w/ 2-wire light socket, but next time put both hands in and move them around some :thumbsup:, whatever the results are please document it, if solo then a video cam would be good, if not solo then perhaps just a scribe. there is no hazard, right ?
 
FionaZuppa said:
no, lets think like "NEC", we dont know exactly what end users do, this NEC code attempts to cover the hazards the best it can.
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Back then the NEC would not mandate something unless ample statistics and/or lab experimentation existed.


Also, the NEC can not anticipate every single miss-use scenario a person might pull off.


However, in the 60s the CMP (and many others) were becoming aware of their own ignorance regarding 2 wire cords and metal framed tools. People were not mis-using these tools and were getting bit at no fault of their own. Thus, the only reasonable solution to take care 2 wire tools was mandating GFCIs.
 
FionaZuppa said:
no, lets think like "NEC", we dont know exactly what end users do, this NEC code attempts to cover the hazards the best it can.


try again, but next time put both hands in and move them around some :thumbsup:
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The experiment was not about NEC, not about GFCI's, not about equipment grounding, it was about how much current would flow through the victim in a specific set of circumstances. Your meter probes were not connected to an appropriate victim in those circumstances. The resistance through the meter as you set it up would be a pretty low resistance path compared to a victim in similar position across the measured points.
 
FionaZuppa said:
try again w/ 2-wire light socket, but next time put both hands in and move them around some :thumbsup:, whatever the results are please document it, if solo then a video cam would be good, if not solo then perhaps just a scribe. there is no hazard, right ?
Click to expand...


Or a hair dryer. The amount of exposed metal would create even larger voltage gradients. However, a missing EGC was a far more common experience.
 
kwired said:
The experiment was not about NEC, not about GFCI's, not about equipment grounding, it was about how much current would flow through the victim in a specific set of circumstances. Your meter probes were not connected to an appropriate victim in those circumstances. The resistance through the meter as you set it up would be a pretty low resistance path compared to a victim in similar position across the measured points.
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stop commenting, pls (until you understand it all). body R in experiment doesnt matter, add in any R value as you see fit, then use experimental data and your wizzy-wig calculator (you dont even need scientific mode) to make inferences. you missed the whole point of the experiment, which was to show that amps can pass across the water and through the body (whatever amps that might be, call them unicorn amps for all i care) w/o ever touching the wires inside the appliance. but then you'll say, "yeah, we already knew that", then i say, "well, then lets make GFCI (whatever that means) at least cover that hazard" --> re-read post #1.

mbrooke said:
Or a hair dryer. The amount of exposed metal would create even larger voltage gradients. However, a missing EGC was a far more common experience.
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:lol::lol::lol:, literally making me laugh,,,,, the real "lol" type,,,,,, stop it :lol::lol::lol:
according to many, there is no hazard to worry about.
 
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